Blade sharpening apparatus

ABSTRACT

In a blade cutting edge sharpening apparatus, pivotal arms carrying an upper and a lower grinding wheel are mounted on a carriage which is horizontally displaceable in respect of the blade and perpendicularly to the cutting edge. Two horizontal pivots extending parallel to the cutting edge support the two arms on the carriage for pivoting in vertical planes about the pivots. The diameters and positions of the grinding wheels form predetermined angles on opposed surfaces of the cutting edge, and the upper arm is adjustable in a horizontal direction relative to the carriage and perpendicularly to the cutting edge for varying the angle of the upper surface of the cutting edge relative to the angle of the lower cutting edge surface.

[4 1 Feb. 11,1975

[ BLADE SHARPENING APPARATUS [75] Inventor: Silvio Repetto, Modena, Italy [73] Assignee: S.p.A. Luigi Rizzi & Co., Modena,

Italy [22] Filed: May 3, 1973 [21] Appl. No.: 356,781

[30] Foreign Application Priority Data May 12, 1972 Italy 24245/72 [52] U.S.C1. 51/247, 69/10 [51] Int. Cl B24b 3/36, B24b 19/00 [58] Field of Search 51/246, 247, 80 R, 80 BS, 51/81 BS, 74 R, 99; 69/10; 83/174 8/1925 Orlow 51/247 9/1950 Hall ....I 69/10 12/1950 Fehlmann 69/10 Primary Examiner-Othell M. Simpson Attorney, Agent, or Firm-Kurt Kelman [57] ABSTRACT In a blade cutting edge sharpening apparatus, pivotal arms carrying an upper and a lower grinding wheel are mounted on a carriage which is horizontally displaceable in respect of the blade and perpendicularly to the cutting edge. Two horizontal pivots extending parallel to the cutting edge support the two arms on the carriage for pivoting in vertical planes about the pivots. The diameters and positions of the grinding wheels form predetermined angles on opposed surfaces of the cutting edge, and the upper arm is adjustable in a horizontal direction relative to the carriage and perpendicularly to the cutting edge for varying the angle of the upper surface of the cutting edge relative to the angle of the lower cutting edge surface.

7 Claims, 10 Drawing Figures PATENTED FEB! 1 I975 SHEEI 10F 5 PATENTED 1 3, 864.880

SHEET 2 OF 5 PATENTED FEB1 1 3.864380 SHEET 30F 5 AIENIEU H 8884.880

SHEEI uOF 5 1 BLADE SHARIENING APPARATUS This invention relates to an apparatus for sharpening the edge of a cutting blade in machines for splitting skins or the like.

It is well known that machines for splitting skins generally have a blade formed of acontinuous strip of material which is tensioned between two end pulleys, one of which is driven so that theblade is longitudinally displaceable and-always presents a new edge for cutting the skin. It is necessary that the cutting edge of the blade in skin splitting machines should be in an exact position and that the angles of the inclined surfaces which form the beveled cutting edge have predetermined values equal to each other or different from each other so as to produce specific thrust effects on the skin during cutting.

Conventional sharpening devices do not permit adjustment of all the parameters relative to either wear of the blade or of the grinding wheels. Furthermore, conventional devices do not permit variation of the angle of the bevel on one side, without changing the diameter of the associated grinding wheel.

It has now been found that by practice of the present invention, the above disadvantages of conventional devices are overcome by providing a sharpening apparatus wherein adjustment of the various sharpening parameters is such that predetermined cutting conditions are maintained.

In accordance with the present invention, there is provided an apparatus for sharpening cuttingblades of skin splitting machines, comprising a carriage displaceable horizontally and perpendicularly to the edge of a cutting blade and having two arms pivoting on horizontal axes parallel to the blade. The free end of these arms each carry a grinding wheel, the diameter and position of which, relative tothe blade, is such so as to form predetermined cutting angles on opposed surfaces of the bevel of the blade. The arms are vertically displaceable, the upper arm being also adjustable ina horizontal direction perpendicularly to the blade, thereby allowing variation of the angle of the bevel of the upper surface of the blade relative to the angle of the bevel on the lower surface of the blade.

The present apparatus includes a pair of grinding wheels of most any suitable type which are horizontally and vertically displaceable dependent on the angles required for the bevel of the cutting edge of the blade, wear of the grinding wheels and wear of the blade. Means are provided for detecting the wear of the grinding wheels and of the blade and for controlling the advance of the grinding wheels and the blade in order to maintain'the cutting edge and the angles of the bevel at predetermined values for each type of process.

Each center of rotation of the grinding wheels has a horizontal axis parallel to the cutting edge of the blade, whereby movement of the grinding wheel by means of a swivel arm is substantially vertical.

The arm carrying the upper grinding wheel may be displaced relative to the carriage in a direction perpendicular to the edge of the blade. This displacement may be obtained, for example, by means of an eccentric pivot, an eccentric support for the pivot, by a slide guide for the swivel or the like, which means of movement may be variable micrometrically on an easily read scale.

In addition, the upper grinding wheel is preferably of a diameter different from that of the lower wheel and also of a lesser abrasive value.

The horizontal movement of the carriage carrying both grinding wheel arms, and vertical movement of each grinding wheel, may be manually controlled relative to the initial position of the sharpening apparatus with respect to the blade. Similarly, the horizontal movement of the upper grinding wheel arm may be manually controlled for determining the upper cutting bevel of the blade.

Vertical movement of the two grinding wheels compensates for the wear on the blade and may be carried out either manually and independently of each other, or automatically relative the advancing movement of the blade. Because it is necessary in order to sharpen the cutting edge of the blade efficiently, a constant pressure must be maintained between the grinding wheel and the blade which depends both on the relative position of the blade to the periphery of the grinding wheels and on the dimensions thereof.

Since, however, both the grinding wheels and also the blade are subjected to wear, it is necessary to increase the relative advance of these parts. This increase cannot be simultaneous with all the working members, but must be divided into different times relative to the different degrees of wear of these parts.

Also, according to the present invention, electrical and hydraulic means are provided for obtaining and controlling the advancing movements of the blade relative the advance of the grinding wheels, all independent of the position of the edge of the blade.

A magnetic detector is provided which is disposed near the cutting blade. The magnetic detector emits signals as soon as the blade recedes by a certain amount from a required position. These signals, suitably amplifled, operate an electric and a hydraulic circuit connected to the means controlling the advance of'the blade, such as, for example, a toothed wheel with a pawl connected to a shaft for controlling the transverse displacement of the blade. When the blade has reached the predetermined position, the magnetic detector interrupts the advancing movement of the blade and energizes a drive for advancing the grinding wheels. This latter excitation is retarded, however, for a certain predetermined time during which both the blade and the grinding wheels remain stationary in position.

The grinding wheels are then displaced vertically by means which may be controlled by a hydraulic system by way of toothed wheels and pawls. The advancing means for the compensation of wear comprises, in addition to the magnetic detector, an electrical control means, hydraulic valves and hydraulic driving means formed by cylinders and pistons, all arranged in a particular manner to be described hereinafter.

Practice of the present invention will be further described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 shows a side view of the present apparatus with portions shown partly in section;

FIG. 2 shows a front view of the apparatus of FIG. 1 with parts in section taken on the line IlII thereof;

FIG. 3 shows a plan view of the apparatus with parts in section and taken along the lines III-III of FIG. 2;

FIG. 4 shows a fragmentary view of the lifting point of the present apparatus;

FIG. is a diagrammatical view of the relative position of the grinding wheels and the cutting blade;

FIG. 6 is a partial view of the device for regulating horizontal position of the upper grinding wheel;

FIGS. 7, 8 and 9 illustrate the corresponding portions of FIGS. 4, 5 and 6 respectively, except in different value position; and

FIG. shows a diagrammatical control diagram for the advance of the blade and the grinding wheels for compensating the wear on these parts.

With reference to FIGS. 1, 2 and 3, the apparatus includes carriage 1 sliding by way of guide la on base 2 in a horizontal edge and perpendicular to the direction of'cutting blade 3. Cutting blade 3 is mounted horizontally displaceably in fixed support 4 which is connected to the base 2. Blade 3 abuts plate 5 which is movable to displace the blade by means of screw 6 manually operable by an external knob 7 or automatically by spindle 8 extending parallel to the blade edge and a pair of meshing toothed wheels 9 and 10. This structure is generally conventional.

For automatic control, spindle 8 is connected to a gearwheel having teeth 8a and controlled by the reciprocal pawl 8b of hydraulic cylinder 80.

Mounted on carriage l are supports 11 and 12 which hold pivots I3 and 14 for grinding wheel-carrying arms 15 and 16 respectively.

As may be seen more particularly from FIGS. 2 and 3, bearings 17 and 18 are interposed between pivot 13 and arm 15. Similarly, bearings 19 and 20 are interposed between pivot 14 and arm 16.

Mounted on each of the arms 15 and 16 are mandrels 21 and 22, respectively, which carry grinding wheels 23 and 24, and are driven by motors 25 and 26 by transmission belts 27 and 28. The assembly of motor, transmission, mandrel and grinding wheel is mounted on each arm 15 and 16 and is pivotable therewith around the respective pivots l3 and 14. As shown in FIG. 1, grinding wheel 24, mounted on upper arm 16, is disposed above blade 3 whereas grinding wheel 23, mounted on the arm 15, is disposed below blade 3.

FIG. 2 also shows that the two grinding wheels are placed apart longitudinally relative to each other in the direction of the cutting edge of blade 3. According to one feature of the present invention, the center portion of pivot 14 of the grinding wheel-carrying arm 16 is eccentric to the two pivot ends 14a and 14b while being coaxial with the bore in support 12. This eccentricity is indicated by e in FIG. 2. The end 14a of eccentric pivot 14 is provided with a graduated disc 29 which is connected to the pivot so as to rotate with it while being locked thereon by nut 30 having prismatic periphery 140, which may be hexagonal in shape, for example. Screws 31 affix stationary indicator 32 on support 12 for cooperation with disc 29 which is rotatable with pivot 14. The carriage l, on which the two pivotable grindstone carrying arms 15 and 16 are mounted, may be horizontally displaced in a direction perpendicular to the cutting edge of blade 3 by movement along guide 1a. This horizontal displacement is controlled by threaded spindle 33 which is mounted on base 2. Spindle 33 is rotatable by means of hand wheel 34 and engages a correspondingly threaded bore in a pole member of sliding carriage 1.

Each swivel arm 15 and 16 may be raised or lowered by rotating it relative to associated pivots 13 and 14 by an externally controlled driving means.

In the embodiment shown, toothed wheel 35 is provided with handle 36 (FIGS. 1 and 3) and is connected to shaft 37 which, by way of intermeshing gears 38, raises or lowers threaded spindle 39 on which an extension of arm 15 rests by way of roller 40.

The same mechanism is provided for pivoting of arm 16, this latter mechanism having a toothed wheel 41 which is provided with handle 42.

The gear wheels 35 and 41 are provided on the periphery with teeth or the like which engage with the respective reciprocal pawls 43 and 44 of hydraulic cylin der 45 and 46 and thereby automatically control the rotations of the gearwheels.

Connected to carriage 1 is arm 47 carrying graduated rod 48 for indicating the relative position of the carriage 1 to the cutting edge of blade 3.

FIGS. 4 to 9 show schematically and on a magnified scale, both details of graduated rod 48 and blade 3 (FIGS. 4 and 7); details of graduated disc 29 which is connected to eccentric pivot 14; and the hexagonal end 14c thereof with reference to the fixed indicator 32 (FIGS. 6-9).

FIG. 5 shows the position of grinding wheels 23 and 24 relative to blade 3 for the settings shown in FIGS. 4 and 6, whereas FIG. 8 shows the position of the grinding wheel relative to blade 3 for the settings indicated in FIGS. 7 and 9.

The operation of the apparatus is as follows:

The lower grinding wheel 23 processes the lower side of the bevelled cutting edge of the blade 3 and is of greater diameter than the upper grinding wheel 24 which processes the upper side of the cutting edge.

Assuming that the cutting edge of blade 3 has been brought to the correct position for grinding by knob 7 and associated abutting plate 5, which operation may alternatively be effected by spindle 8, the assembly of carriage 1 is brought near the cutting edge of the blade with a horizontal movement obtained by operating hand wheel 34, until the position of the lower grinding wheel 23, relative to the blade 3, gives the desired incline of the lower surface of the cutting bevel, for example 8 (see FIG. 5.). In this position, graduated rod 48, connected to the carriage 1, directly indicates, by means of the graduations, the angle of the lower bevel produced by the grinding wheel, rather than the value of the horizontal displacement of the slide, i.e., the position of the lower grinding wheel relative to the blade.

It follows that the horizontal adjustment of carriage 1, operated by the hand wheel 34, makes it possible to vary the angle of the lower bevel. This value may be read directly from graduated rod 48. The upper grinding wheel 24, supported by pivotal arm 16, may be so disposed in a position relative to the lower grinding wheel 23 that the angle of the upper surface of the bevel produced by the associated grinding wheel is equal to the angle of the lower surface. This position is achieved by pivotally displacing the upper arm 16 relative to carriage l by the rotation of horizontally extending, eccentric pivot 14.

The pivotal position of the upper arm, adjusted to make the angle of the bevel produced by the upper grinding wheel equal to that produced by the lower grinding wheel, is indicated in the graduation of disc 29, i.e., reference position 0. It is thus understood that the difference between the two angles of the bevel is 0.

Using the hexagonal nut to rotate the eccentric pivot 14 relative to the support 12, the assembly of the grinding wheel carrying arm 16 is displaced towards the edge of the blade 3, whereby the grinding wheel 24 (FIG. 8) meets the blade 3 at an angle less than the pre-' ceding angle. The difference between these two is shown directly in an angular value on the graduated disc 29. In the example shown in FIG. 9, the difference in the angular values is 2 relative to the angle of the lower side detected by the graduated rod 48, whereby the upper side of the bevel is inclined by 6.

When the working position of the two grinding wheels and of the blade is stabilized, the increase in the advance both of the grinding wheels and of the blade is obtained automatically by the circuit shown schematically inFlG. 10. In FIG. the wheels are shown with saw teeth and associated pawls for controlling the advances.

With reference to FIG. 10, cutting blade 3 is disposed very close to magnetic detector 50. The magnetic detector is adjusted to emit a predetermined signal while the edge of the blade is approaching a predetermined working position and a different predetermined signal when this position is reached. The signal emitted by magnetic detector 50 is amplified by electronic amplifier 51, which is in series connection with a common electric amplifier 52.

The situation shown in FlG. 10 corresponds to that in which blade 3 has not yet reached the predetermined position. Under these conditions the signal of the detector 50, amplified by circuit 51, passes to the relay 53 which controls two.circuit breakers 53a and 53b. The first of these switches, i.e., 53a, is closed when supplying current to solenoid 54 which controls valve 55 of a hydraulic circuit. The hydraulic circuit comprises a reciprocating mechanical distributor valve 56 which is controlled by eccentric 57 which is further associated with the motor of the machine, pipes 58 and 59, and the double-acting cylinder and piston unit 8c connected to pawl 8b which controls gear wheel 8a.

It follows then that mechanical valve 56 continuously reverses the feed to cylinder 80 and pawl 8b rotates wheel 8a connected to the shaft 8. Thus, the blade has to advance as a result of the associated means of wheels 9 and 10, plate 5 and screw 6 as already mentioned. When the edge of the blade reaches the predetermined position, magnetic detector 50 emits a different predetermined signal, whereby circuit breaker 53b closes and 53a opens under the control of relay 53.

Consequently, further advance of the blade is stopped by de-energization of solenoid 54 and instead,

' relay 60 is energized. However, relay 60 does not immediately close circuit breaker 60a connected thereto, but is adjusted so as to retard, for a certain time T1, the closing of the circuit breaker. During this period of time T1, there is no advance either of the blade or of the grinding wheels.

When the time T1 has passed, relay 60 closes the circuit breaker 60a which, by means of conductor 61, forms a closed circuit. Switch 62a of relay 62, through conductor 63, excites relay 64 carrying the circuit breakers 64a and 6411, both being normally open.

The relay 64 also operates with a retarded action for a period T2, When this period T2 has passed, the relay 64 closes the circuit breakers 64a and 64b, whereby the former excites, through conductor 65, a relay 66 and the second excites relay 62 whose circuit breaker 62a is normally closed. The relay 62 operates, however, with a retarded action for a time T3, after which it interrupts circuit breaker 62a and hence circuit 61, 63, de-energizing relay 64 which reopens contacts 64a and 64b. During time T3 in which relay 62 has remained inactive, the relay 66 has actuated valve 66a which feeds, by way of pipes 67 and 68, hydraulic fluid under pressure to hydraulic cylinders 45 and 46, thus actuating pawls 43 and 44. The pawls in turn produce rotation of toothed wheels 35 and 41, causing advance of the grinding wheels, by means of shaft 37, gears 38, spindle 39 and roller 40, as described, thereby compensating for wear.

When, as stated, time T3 has passed, retarded relay 62 opens its circuit breaker 62a interrupting the excitation of the relays 64. It follows then that relay 66 and relay 62 are also de-energized and the latter returns to its position of rest in which the circuit breaker 62a is closed, then exciting relay 64 through conductor 63. The latter, as already stated, is retarded in its operation for time period T2, whereby, when this time has passed, the already stated cycle is repeated, with the consequence that hydraulic units 45 and 46 impose reciprocating movements on pawls 43 and 44 with every interval of time due to the delayed operation for the relays 62 and 64, i.e., for the time periods T2 T3. By result of these movements, grinding wheels 23 and 24 are vertically displaced in opposite directions in order to approach the blade and perform the sharpening operation. However, this sharpening operation produces wear on the blade whereby the cutting edge is reduced relative to the first predetermined position. This reduction is determined by detector 50, which emits a signal for exciting relay 53 which is returned to the position shown in FIG. 10. Thus, de-energizing is effected, coupled with opening of circuit breaker 53b, with relay in turn opening circuitbreaker 60a, thereby interrupting the advance of the grinding wheels and actuating advance of the blade by closing the already described associated electrical, mechanical and hydraulic circuit which is operated by circuit breaker 53a. Thus, the cycles of the advance of the blade following wear resulting from sharpening, and advance of the grinding wheels because of wear during grinding, are repeated alternately. The alternating advance movement is regulated by the circuit of FIG. 10.

It is to be understood that numerous variations may be made to the above described invention, depending on the requirements of construction and the known means employed, without departing from the scope of the present invention.

What is claimed is:

1. An apparatus for sharpening the cutting edge of a blade, comprising the combination of l. a support for the blade,

2. a carriage mounted for displacement horizontally in respect of the blade on the support and perpendicularly to the cutting edge of the blade,

3. means for displacing the carriage,

4. an upper and a lower arm pivotally mounted on the carriage for horizontal displacement therewith perpendicularly to the cutting edge of the blade,

5. two horizontal pivots extending substantially parallel to the cutting edge of the blade for pivotally supporting the two arms on the carriage,

6. means for pivoting the arms in respective vertical places about the respective pivots,

7. an upper and a lower grinding wheel respectively carried by a free end remote from the respective pivot of the upper and lower arm,

a. the diameters and positions of the grinding wheels forming predetermined angles on opposed surfaces of the cutting edge of the blade, and

8. means for adjusting the upper arm in a horizontal direction relative to the carriage and perpendicularly to the cutting edge of the blade for varying the angle of the upper surface of the cutting edge relative to the angle of the lower surface of the cutting edge.

2. The blade cutting edge sharpening apparatus of claim 1, further comprising means for detecting the position of the cutting edge of the blade relative to the position of the grinding wheels.

3. The blade cutting edge sharpening apparatus of claim 1, wherein the means for adjusting the upper arm comprises eccentric means on the horizontal pivot for the upper arm, and further comprising a graduated indicator means on the pivot for detecting the adjustment on rotation of the pivot.

4. The blade cutting edge sharpening apparatus of claim 1, further comprising means for detecting the extent of the horizontal displacement of the carriage in respect of the blade on the support.

5. The blade cutting edge sharpening apparatus of claim 1, wherein the means. for pivoting the arms comprises manually operable gear means.

6. The blade cutting edge sharpening apparatus of claim 1, wherein the means for pivoting the arms comprises gear means, hydraulic actuating means for operating the gear means, and an electric control circuit for actuating the hydraulic actuating means.

7. The blade cutting edge sharpening apparatus of claim 1, further comprising means for horizontally displacing the blade on the support relative to the grinding wheels to compensate for wear of the grinding wheels and the cutting edge during grinding, the horizontal displacing means of the blade comprising a detector detecting the relative position of the cutting edge of the blade, means actuating the horizontal displacing means of the blade in response to the detection of a receding position of the cutting edge due to wear, and means controlling the pivotal movement of the arms in response to wear of the grinding wheels, and control means for coordinating the actuating means and the controlling means. 

1. An apparatus for sharpening the cutting edge of a blade, comprising the combination of
 1. a support for the blade,
 2. a carriage mounted for displacement horizontally in respect of the blade on the support and perpendicularly to the cutting edge of the blade,
 3. means for displacing the carriage,
 4. an upper and a lower arm pivotally mounted on the carriage for horizontal displacement therewith perpendicularly to the cutting edge of the blade,
 5. two horizontal pivots extending substantially parallel to the cutting edge of the blade for pivotally supporting the two arms on the carriage,
 6. means for pivoting the arms in respective vertical places about the respective pivots,
 7. an upper and a lower grinding wheel respectively carried by a free end remote from the respective pivot of the upper and lower arm, a. the diameters and positions of the grinding wheels forming predetermined angles on opposed surfaces of the cutting edge of the blade, and
 8. means for adjusting the upper arm in a horizontal direction relative to the carriage and perpendicularly to the cutting edge of the blade for varying the angle of the upper surface of the cutting edge relative to the angle of the lower surface of the cutting edge.
 2. The blade cutting edge sharpening apparatus of claim 1, further comprising means for detecting the position of the cutting edge of the blade relative to the position of the grinding wheels.
 2. a carriage mounted for displacement horizontally in respect of the blade on the support and perpendicularly to the cutting edge of the blade,
 3. means for displacing the carriage,
 3. The blade cutting edge sharpening apparatus of claim 1, wherein the means for adjusting the upper arm comprises eccentric means on the horizontal pivot for the upper arm, and further comprising a graduated indicator means on the pivot for detecting the adjustment on rotation of the pivot.
 4. an upper and a lower arm pivotally mounted on the carriage for horizontal displacement therewith perpendicularly to the cutting edge of the blade,
 4. The blade cutting edge sharpening apparatus of claim 1, further comprising means for detecting the extent of the horizontal displacement of the carriage in respect of the blade on the support.
 5. The blade cutting edge sharpening apparatus of claim 1, wherein the means. for pivoting the arms comprises manually operable gear means.
 5. two horizontal pivots extending substantially parallel to the cutting edge of the blade for pivotally supporting the two arms on the carriage,
 6. means for pivoting the arms in respective vertical places about the respective pivots,
 6. The blade cutting edge sharpening apparatus of claim 1, wherein the means for pivoting the arms comprises gear means, hydraulic actuating means for operating the gear means, and an electric control circuit for actuating the hydraulic actuating means.
 7. The blade cutting edge sharpening apparatus of claim 1, further comprising means for horizontally displacing the blade on the support relative to the grinding wheels to compensate for wear of the grinding wheels and the cutting edge during grinding, the horizontal displacing means of the blade comprising a detectOr detecting the relative position of the cutting edge of the blade, means actuating the horizontal displacing means of the blade in response to the detection of a receding position of the cutting edge due to wear, and means controlling the pivotal movement of the arms in response to wear of the grinding wheels, and control means for coordinating the actuating means and the controlling means.
 7. an upper and a lower grinding wheel respectively carried by a free end remote from the respective pivot of the upper and lower arm, a. the diameters and positions of the grinding wheels forming predetermined angles on opposed surfaces of the cutting edge of the blade, and
 8. means for adjusting the upper arm in a horizontal direction relative to the carriage and perpendicularly to the cutting edge of the blade for varying the angle of the upper surface of the cutting edge relative to the angle of the lower surface of the cutting edge. 